1. Field of the Invention
The present invention relates to a synchronization system of a manual transmission, and more particularly to a dual synchronization system of a manual transmission having two sets of a plurality of keys for synchronization.
2. Brief Description of the Prior Art
In general, an automatic transmission is installed between clutch and driving axle, playing a role to change rotational force of an engine depending on a running condition of a vehicle and convey it to the driving axle and including a backward running apparatus for driving the vehicle backward.
The aforementioned transmission is largely classified into an automatic transmission that automatically changes speed and a manual transmission that a driver directly manipulates shifting levers to four levels of forward driving or a level of backward driving. Specifically, the invention relates to a dual synchronization system of the manual transmission.
FIG. 1 illustrates a synchronization system of a general manual transmission for an instance. As shown in the drawing, the synchronization system 1 includes a synchronizer sleeve 13, synchronizer spring 15, synchronizer hub 7, synchronizer key 11 and synchronizer ring 35, all of which are involved to overcome a difference in rotational speed between the synchronizer hub 7 and a clutch gear (not shown) in their connection or disconnection.
In other words, the synchronizer hub 7 and the clutch gear having different rotational speeds will be connected together in the following steps. When the synchronizer sleeve 13 slides on the synchronizer hub 7 to a rotating direction of its rotational axle, the synchronizer key 11 closely attached into the synchronizer sleeve 13 with the synchronizer spring 15 pushes the synchronizer ring 35 tightly to the clutch gear. As a result, the synchronizer ring 35 and the clutch gear offset the difference in their rotational speeds for synchronization. At this time, the synchronizer sleeve 13 further proceeds to pass the synchronizer ring 35 and meshed with the clutch gear, so as to get the synchronizer hub 7 and the clutch gear to be in their direct connection.
However, in the synchronization system 1 thus constructed, when the synchronizer sleeve 13 passes the synchronizer ring 35 and proceeds to the clutch gear after synchronization of the synchronizer ring 35, the synchronizer sleeve 13 pushes the synchronizer key 11 attached to the internal side thereof with the synchronizer spring 15 inwards and over, so that the synchronizer key 11 can no longer provide force to push the synchronizer ring 35 tightly to the clutch gear.
Therefore, at the aforementioned states, no force is involved to push the synchronizer ring 35 closely to the clutch gear while the synchronizer sleeve 13 passes the synchronizer ring 35 and meshes with the clutch gear. At this time, a breakdown of synchronization occurs to bring about a second nibble, which is a disadvantage in the conventional synchronization system.
It is an object of the present invention to solve the aforementioned problems and to provide a dual synchronization system of a manual transmission to prevent breakdown of synchronization and improve its shifting feeling of an auto vehicle.
In order to accomplish the aforementioned object of the present invention, there is provided a dual synchronization system of a manual transmission constructed with first and second key sets respectively having a plurality of keys that are positioned apart at a predetermined degree of angle along the circumferential direction of a synchronizer ring, the first key set closely attaching the synchronizer ring to a clutch gear at the initiation of synchronization and the second key set pushing the synchronizer ring to the clutch gear after the completion of synchronization, thereby continuously keeping frictional force between the synchronizer ring and the clutch gear.